An apparatus of the type mentioned before is known from U.S. Pat. No. 3,930,535. In this known apparatus the formulation, which is an ice-mix, flows from a storage container through the feed pipe into the inlet chamber of the cooling and freezing cylinder. There, air forced into the inlet chamber is whipped into the formulation so that the ice-mix/air mixture is frozen and then drawn off through a discharge valve as a portion of ice-cream, particularly as what is known as soft ice. The feed pipe which is formed by a tube of relatively large cross-section discharges laterally into the inlet chamber so that compressed air is present above the space in the outlet orifice of the feed pipe. This permits a control of the supply of the ice-mix from the container to the cylinder. In this known apparatus of the type in question, outside of the actual ice-cream producing process, the ice-mix is heated up in the cooling and freezing cylinder and in the storage container to pasteurisation temperature. It is an experience that ice-mix emerging from the inlet chamber and enriched with air and already partly frozen, rises through the feed pipe into the storage container where it leads to a considerable amount of foaming. This also causes breakdown since the ice-mix which is not yet enriched with air no longer properly flows into the inlet chamber so that when ice portions are drawn off at the discharge valve there is the risk that air flows out through the discharge valve.
It is known that this foaming can be partly countered by an appropriate composition of the formulation (ice-mix) used. Where the composition of the formulation cannot be affected, however, this is not possible.